Conventional devices for monitoring the characteristics of circuit breakers monitor opening time, which is the time between the output of a command during the operation of the circuit breakers and opening of circuit breaker contacts; closing time, which is the time between the output of a command and closing of the circuit breaker contacts; opening speed, which is the speed during the time between the start of movement of the circuit breaker contacts and opening; and closing speed, which is the speed during the time between the start of movement of the circuit breaker contacts and closing. For example, in the invention described in Patent Literature 1, opening time is finely divided, and the change during each time period after the division is monitored to detect any abnormality in the circuit breaker. Patent Literature 2 discloses an invention in which the rising point and the minimum point of a control current waveform at power-on, and an operation starting point, a predetermined-angle rotating point, and a total-angle rotating point of a rotational operating shaft are detected, and the time and the distance between the points are compared with reference values, thereby obtaining an indication of any abnormality in the circuit breaker.